Extensive felling and mulching operations are often performed with a heavy-duty brush cutter mounted to the front of a self-propelled vehicle. A typical brush cutter includes a brush cutting head with a cylindrical support body, or drum, and a plurality of mounting blocks welded or fastened to the outer surface of the support body. Cutting teeth are mounted on the front leading face of each mounting block, typically through the use of a nut and bolt combination. High velocity rotation of the drum causes the cutting elements to shred wood, debris and the like.
Mounting blocks for the cutting teeth on cutting heads are also often fixedly mounted on the surface of the cylindrical support head in an exposed position. An example is shown in U.S. Pat. No. 5,873,534. These mounting blocks, and/or the teeth fixedly mounted on them, often hit rocks or large trees and are damaged or even broken off. Replacement of these mounting blocks is difficult and expensive. Over relatively short periods of use, one or more of the teeth typically break off, while others soon become too worn for effective cutting and mulching. Breakage of a single tooth during operation of the cutting head can cause substantial damage to the cutting head and presents a considerable safety hazard to nearby workers.
Protective means may be provided in front of each mounting block to prevent the blocks from directly striking rocks or large trees during operation of the cutting head. Thus the blocks are not subjected to sudden large forces which could result in serious damage. Examples include protective collars encircling the cylindrical support base. These collars typically stop just short of the mounting block in order to provide a clearance space, while the opposing end of the collar may be welded to the back face of the associated mounting block.
One such brush cutting head is described in U.S. Pat. No. 6,764,035. This patent discloses a brush cutting head that has a cylindrical support base and a plurality of cutting tooth mounting blocks fastened to the outer surface of the base. The bottom surface of each mounting block is concavely curved to match the radius of the base thereby allowing each mounting block to be welded onto the base with its bottom surface flush with the outer surface of the base. Each mounting block carries a cutting tooth on its front face. To protect the mounting blocks from rocks, each mounting block is provided with a protective collar. Each protective collar is welded to the outer surface of the base and extends radially therefrom, transverse to the longitudinal axis of the base. Each collar terminates circumferentially a short distance from the front face of the mounting block with which it is associated to provide a front clearance space. The opposed end of the collar is welded to the back face of the associated mounting block to strengthen it.
While the protective collars described in U.S. Pat. No. 6,764,035 afford the cutting tooth assemblies some protection, the cutting teeth remain nonetheless exposed to violent impact with hard objects, like stones, and thus are still vulnerable to damage during brush cutting operations.
Another example of one such brush cutting head is described in United States Patent Publication No. 2010/0044487. This published patent application discloses a brush cutter that has a cylindrical support base and a plurality of mounting blocks fastened to the outer surface of the base. The bottom surface of each mounting block is concavely curved to match the radius of the base thereby allowing each mounting block to be welded onto the base with its bottom surface flush with the outer surface of the base. Each mounting block has a front face which is recessed from the front end of the mounting block so as to define a horizontal shelf near the bottom surface of the mounting block. Each mounting block carries a cutting tooth on its front or leading face. The cutting tooth is fastened to the mounting block by a nut and bolt combination, the bolt being inserted through a smooth bore defined in the mounting block.
However, the design of the cutting tooth for this brush cutting head tends to suffer from certain disadvantages. Manufacture of the guide members projecting from the base portions of the cutting tooth must be precise and can be time consuming. Moreover, certain problems have been encountered when replacing old, broken or worn cutting teeth on the brush cutting head. In some cases, it has been found that the guide members projecting from the base portions of replacement cutting teeth do not always line up with the fittings on the mounting block into which they are to be received. As a result of this misalignment, some cutting teeth could not be properly secured to the mounting blocks, thereby causing delay, excessive warranty claims and requiring operators to carry on hand a greater number of replacement cutting teeth than would ordinarily be required.
United States Patent Application Publication No. 2007/0261763 describes a brush cutting head provided with differently configured collars and cutting tooth assemblies. This brush cutting head has a cylindrical support body with a curved outer surface and a plurality of penannular collars. The collars are mounted to the support body at spaced apart locations and extend radially from its curved outer surface. Each collar cooperates with an adjacent collar to define a mounting station between adjacent collars. A plurality of cutting tooth assemblies are carried on the outer surface of the support body. Each cutting tooth assembly has a cutting tooth for placement within a mounting station, and a mounting assembly engageable with the adjacent collars to secure the cutting tooth in the mounting station.
By having the cutting tooth and its associated mounting assembly disposed between adjacent collars, two-fold protection is afforded to the cutting teeth. The collars shield the cutting teeth from rocks and other hard objects and reduce the stresses to which the cutting teeth are subjected during operations by improving the distribution of forces through the mounting assembly.
While the brush cutting head described in United States Patent Application Publication No. 2007/0261763 has proven itself successful on the field and constitutes an improvement over what was previously available on the market, efforts continue to be made to lengthen the service life of the cutting teeth and their mounting assemblies by reducing the incidence of destructive impact with rocks.
Additional cutting heads are described in U.S. Pat. No. 7,810,531, and U.S. Patent Publication No. 2013/0099039; all of the aforementioned patents and publications being incorporated herein by reference. The cutting teeth on brush cutters are often designed and mounted on the mounting blocks on the cutting head to cut in a tangential direction when the cylindrical support head is rotated. As a result, the mounting blocks are subject to high shear forces. The blocks must be quite large to resist these forces and this adds weight to the cutting head increasing power requirements. The teeth employed are also usually quite complicated in construction and are quite costly to replace when broken or damaged.
Furthermore, as the cutting head rotates to cut through wood and the like, wood chips and debris tend to build up underneath the cutting teeth and in-between the mounting block and protective collars, causing detrimental effects to both the cutting assembly and cutting performance. This build-up of wood debris decreases cutting efficiency of the cutting head, thus requiring more energy to perform the cutting process. Additionally, the effectiveness of each cut is decreased due to wood build-up underneath the cutting portion of the teeth. As wood is impacted and pushed against the cutting assembly, components of the assembly become blunted and worn-down over time.
In light of the foregoing, it would be advantageous to provide a cutting head, specifically cutting teeth, which exhibit improved wear resistance characteristics. In particular, teeth which do not require frequent sharpening, repair or replacement would be most desirable. It would be further advantageous to provide a self-cleaning cutting assembly that cuts and cleans the teeth concurrently or sequentially, thus preventing the build-up of debris along the cutting head.